<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    var obj = {
      age: 18,  // 键  值 对 
      username: 'zs',
      address: '济南'
    }

    // console.log( obj['age'] )
    // console.log( obj['username'] )
    // console.log( obj['address'] )

    // for(var key in obj) {
    //   console.log( key )
    //   console.log( obj[key] )
    // }
  </script>
</body>
</html>